1. Field of the Invention
The present invention relates to an organic light emitting diode (OLED) device, and more particularly, to an OLED device which has excellent durability, long life-time, and increases internal efficiency through balanced electron and hole injection by doping an insulator into or stacking an insulator on at least a part of an organic thin layer formed between an anode and an emission layer and between an emission layer and a cathode.
2. Discussion of Related Art
A conventional OLED device has a structure in which an emission layer is formed between an anode and a cathode, a first organic thin layer is formed between the anode and the emission layer, and a second organic thin layer is formed between the emission layer and the cathode. Here, when a voltage is applied from the outside, a hole is transported to the emission layer through the first organic thin layer from the anode, and an electron is transported to the emission layer through the second organic thin layer from the cathode, thereby generating an exciton in the emission layer and transferring the exciton from an excited state to a ground state to emit light.
FIG. 1 is a cross-sectional view of a conventional OLED device.
Referring to FIG. 1, an OLED device is formed by sequentially stacking an anode 20, a first organic thin layer A, an emission layer 50, a second organic thin layer B and a cathode 90 on a substrate 10.
The first organic thin layer A includes a hole injection layer 30 which has good hole injection properties, and a hole transport layer 40 which has good hole transport properties. And, the second organic thin layer B includes a hole blocking layer 60 which prevents hole pass, an electron injection layer 80 which has good electron injection properties, and an electron transport layer 70 which has good electron mobility properties. Theses layers are formed in the form of a thin film to facilitate injection of holes and electrons.
In such a conventional OLED device, the holes and electrons injected from both electrodes create excitons in the organic emission layer and then the excitons transition from an excited state to a ground state to emit light. However, it has problems of leakage current, non-uniform brightness and a short life-time of the device, which are caused by non-uniformity of charge due to a difference in mobility between the hole and the electron.
Accordingly, there is a continuous need for research and development on an OLED device that has high luminous efficiency, high durability and long life-time. Therefore, OLED devices are being improved in structure and material.
In the present invention, the inventors provide an OLED device having high internal efficiency, excellent durability and long life-time through balanced charge (hole or electron) injection by doping or stacking at least a part of a first organic thin layer between an anode and an emission layer or a second organic thin layer between an emission layer and a cathode constituting the OLED device using a predetermined insulator to have an appropriate concentration or thickness.